Aerospace devices and implantable medical devices such as pacemakers, defibrillators, speech processors, left ventricular assist devices (LVAD), and neurostimulators have many stringent requirements. They must be small and lightweight, and must therefore have high energy density batteries to provide adequate capacity with long cycle life and long calendar life. For aerospace applications, good low temperature performance is also needed, and for implantable medical devices, good body temperature performance is also needed.